Add variable slice support and prompts

StabilityMatrix.Avalonia/Models/Inference/FileNameFormatProvider.cs

@@ -25,6 +25,8 @@ public partial class FileNameFormatProvider
         _substitutions ??= new Dictionary<string, Func<string?>>
         {
             { "seed", () => GenerationParameters?.Seed.ToString() },
+            { "prompt", () => GenerationParameters?.PositivePrompt },
+            { "negative_prompt", () => GenerationParameters?.NegativePrompt },
             { "model_name", () => GenerationParameters?.ModelName },
             { "model_hash", () => GenerationParameters?.ModelHash },
             { "width", () => GenerationParameters?.Width.ToString() },
@@ -47,11 +49,20 @@ public partial class FileNameFormatProvider
         var matches = regex.Matches(format);
         var variables = matches.Select(m => m.Groups[1].Value);
 
-        foreach (var variable in variables)
+        foreach (var variableText in variables)
         {
-            if (!Substitutions.ContainsKey(variable))
+            try
             {
-                return new ValidationResult($"Unknown variable '{variable}'");
+                var (variable, _) = ExtractVariableAndSlice(variableText);
+
+                if (!Substitutions.ContainsKey(variable))
+                {
+                    return new ValidationResult($"Unknown variable '{variable}'");
+                }
+            }
+            catch (Exception e)
+            {
+                return new ValidationResult($"Invalid variable '{variableText}': {e.Message}");
             }
         }
 
@@ -80,9 +91,38 @@ public partial class FileNameFormatProvider
             }
 
             // Now we're at start of the current match, add the variable part
-            var variable = result.Groups[1].Value;
+            var (variable, slice) = ExtractVariableAndSlice(result.Groups[1].Value);
+            var substitution = Substitutions[variable];
 
-            parts.Add(FileNameFormatPart.FromSubstitution(Substitutions[variable]));
+            // Slice string if necessary
+            if (slice is not null)
+            {
+                parts.Add(
+                    FileNameFormatPart.FromSubstitution(() =>
+                    {
+                        var value = substitution();
+                        if (value is null)
+                            return null;
+
+                        if (slice.End is null)
+                        {
+                            value = value[(slice.Start ?? 0)..];
+                        }
+                        else
+                        {
+                            var length =
+                                Math.Min(value.Length, slice.End.Value) - (slice.Start ?? 0);
+                            value = value.Substring(slice.Start ?? 0, length);
+                        }
+
+                        return value;
+                    })
+                );
+            }
+            else
+            {
+                parts.Add(FileNameFormatPart.FromSubstitution(substitution));
+            }
 
             currentIndex += result.Length;
         }
@@ -110,10 +150,36 @@ public partial class FileNameFormatProvider
         };
     }
 
+    /// <summary>
+    /// Extract variable and index from a combined string
+    /// </summary>
+    private static (string Variable, Slice? Slice) ExtractVariableAndSlice(string combined)
+    {
+        if (IndexRegex().Matches(combined).FirstOrDefault() is not { Success: true } match)
+        {
+            return (combined, null);
+        }
+
+        // Variable is everything before the match
+        var variable = combined[..match.Groups[0].Index];
+
+        var start = match.Groups["start"].Value;
+        var end = match.Groups["end"].Value;
+        var step = match.Groups["step"].Value;
+
+        var slice = new Slice(
+            string.IsNullOrEmpty(start) ? null : int.Parse(start),
+            string.IsNullOrEmpty(end) ? null : int.Parse(end),
+            string.IsNullOrEmpty(step) ? null : int.Parse(step)
+        );
+
+        return (variable, slice);
+    }
+
     /// <summary>
     /// Regex for matching contents within a curly brace.
     /// </summary>
-    [GeneratedRegex(@"\{([a-z_]+)\}")]
+    [GeneratedRegex(@"\{([a-z_:\d\[\]]+)\}")]
     private static partial Regex BracketRegex();
 
     /// <summary>
@@ -121,4 +187,6 @@ public partial class FileNameFormatProvider
     /// </summary>
     [GeneratedRegex(@"\[(?:(?<start>-?\d+)?)\:(?:(?<end>-?\d+)?)?(?:\:(?<step>-?\d+))?\]")]
     private static partial Regex IndexRegex();
+
+    private record Slice(int? Start, int? End, int? Step);
 }